The Tc1-like family of transposons and the retroviral-like transposons are unique for their wide dispersion in diverse organisms. Members belonging to the Tc-1-like family have been characterized in nematodes, diptera, fish and amphibians: Tc1 in Caenorhabditis elegans, TCb1 in Caenorhabditis briggsae, HB1 in Drosophila melanogaster, Uhu in Drosophila heteroneura, Minos in Drosophila hydei, and Tes1 in the Pacific hagfish Eptatetrus stouti. All are characterized by a relative short length (1.6 to 1.8 kb), the presence of inverted terminal repeats, and significant sequence similarity in the region between the repeats.
The Minos-1 transposable element has been identified as a 1775 bp dispersed repetitive sequence inserted within the transcribed spacer in one of the repeats of Drosophila hydei (Franz and Savakis, Nucl. Acids Res. 19: 6646 (Dec. 11, 1991)). The element is characterized by 255-bp long perfect inverted repeats and the presence of two long, non-overlapping open reading frames (ORFs) on the same strand. The longest of the ORFs shows approximately 30% sequence identity with TcA, but does not begin with an ATG codon. It appears, therefore, that the cloned element represents a defective member of the Minos family, as is the case with all previously sequenced Tc1-like elements, with the possible exceptions of Tc1 and Tcb1.
Transposable elements are natural components of genomes ranging from bacteria to vertebrate organisms (Lewin, Genes VI, Chapter 18, Oxford University Press, (1997)). Thus, due to their widespread phylogenetic distribution, evolutionary conservation and genomic mobility, transposons are valuable tools for genetic manipulations, such as, for example, the integration of nucleic acids in germ cells for the production of transgenic animals, and genetic transformation and insertional mutagenesis in somatic cells and viral vectors for use as therapeutics.